Sit-ups can strengthen your belly muscles, but doing them incorrectly can hurt your back. Sit-ups should be done while you lie on your back with your knees bent enough for the soles of your feet to touch the floor. Place both hands on your chest and slowly raise your head off the ground.
All of the popular diet books, regardless of the "scientific" explanations they give, recommend menus that give you 1500-1800 calories or less per day, and for most people this means you will be taking in fewer calories. You can lose weight on any low-calorie diet, but ask yourself: Is this a way of eating I can follow for the rest of my life?
Elastic compression stockings have no effect whatever on exercise, according to a study from France (European Journal of Applied Physiology, July 2006). They neither increase nor decrease endurance, strength, speed, recovery, or blood flow to the limbs.